This invention relates generally to a roll mixing machine and method and, more particularly, to a machine and method for uniformly and efficiently mixing rubber or synthetic resin material used for injection molding, sheet rolling, film rolling, extrusion molding and the like.
Screw mixing machines are used to mix a resin material with a pigment and other additives. Such machines mix uniformly and without unevenness to efficiently obtain a uniform color. However, in cases where a variety of resin materials in small quantities are individually mixed, cleaning of the interior of the screw mixing machine is time consuming and results in reduced periods of machine usage thereby increasing cost. Conversely, conventional roll mixing machines can be easily cleaned and are well suited for mixing small quantities of various materials. However, the mixing efficiency provided by roll machines is poor compared to screw machines so that roll machines require longer mixing periods to obtain uniform color.
In a roll mixing machine disclosed in Japanese Patent Publication No. 57(1982)-30045, a number or rotary cutters are disposed at axially equal intervals frontwardly of a front roller, and a feed blade is centrally inclined downstream of each rotary cutter. A web-like resin material which has been mixed and wound on the front roller is parted widthwise by the cutters, and the parted web-like resin material is biased toward the central portion of the front roller by the feed blades and fed between front and rear rollers.
However, in the aforementioned roll mixing machine, the split web-like resin material is moved only a short distance toward the central portion of the front roller. Thus, for example, a pigment which is present in the right side edge of the web-like resin material is not mixed into the left side edge during each passage of the web-like resin material between the pair of rolls. For that reason considerable time is required to obtain a uniform dispersion of the resin material.